Here we show a case study of plasmon driven electron transfer between gold nanoparticles and fullerene derivative PCBM with pump probe SERS. PCBM is known to have strong electron affinity and is treated as an electron acceptor attached to gold nanoparticles. In cw pump probe SERS experiments, the gold nanoparticles are excited at monomer plasmon resonance with pump laser. The generated hot electrons transferred to PCBM and this electron transfer behavior is monitored by the lower-wavenumber shift of PCBM pentagonal pinch mode (~1460 cm<sup>-1</sup>) in SERS spectra. Pump power and wavelength dependence of this plasmon-driven electron transfer were also demonstrated in pump probe SERS experiments. The peak shift of 1460 cm<sup>-1</sup> mode increased with shorter pump wavelength, indicating the indirect hot electron transfer mechanism. In the DFT calculation, Au nanoparticles are treated with Jellium model and PCBM is considered on atomic level. The wavefunction hybridization of PCBM and Au jellium particle is weak, which also provide a theoretical evidence of indirect electron transfer. Furthermore, the anti-Stokes/Stokes ratio of PCBM SERS spectra proved that there was no significant photothermal or vibrational pumping effect during electron transfer process. Ultrafast ps pump probe SERS experiment on the same system shows that the negatively charged PCBM have a long lifetime.

Probing plasmon-driven electron transfer between gold nanoparticles and PCBM with pump probe SERS

2019 Fall National Meeting

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